tail bitten

As was previously recommended to me via humble fish, I tried new life spectrum thera+a and vitachem which are not helping. I need some help in getting my poor tangs tail fixed. It looks like it was nipped, scratched or something. I've been trying for 90 days and need a new direction to help...

I have a matted filefish that's kept in the sump (has become his home to aggression with other fish). Today I found him lodged at the bottom of the tank due to the spikes on its horn. They were lodged into some filter foam that I use to buffer the protein skimmer. There was a pencil sea urchin...